pH/thermoreversible hydrogels III: Synthesis and swelling behaviors of (N-isopropylacrylamide-co-acrylic acid) copolymeric hydrogels |
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Authors: | Wen-Fu Lee Chih-Hsuan Shieh |
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Affiliation: | (1) Department of Chemical Engineering, Tatung Institute of Technology, Taipei, 10451, Taiwan, Republic of China |
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Abstract: | A series of pH-thermoreversible hydrogels exhibiting volume phase transition were synthesized by three degrees of neutralization
(DN) of acrylic acid (AA) and N-isopropylacrylamide (NIPAAm). The influence of environmental conditions, such as temperature and pH, on the swelling behavior
of these copolymeric gels is investigated in this article. Results show that the negatively charged hydrogels exhibit different
equilibrium swelling ratios at different pH values depending on the ionic composition. The pH-sensitivities of these gels
also strongly depend on the DN of AA in the copolymeric gels. The results show that the higher the DN, the higher the gel
pH-sensitivity. These hydrogels based on a temperature-sensitive hydrogel demonstrate a larger change of equilibrium swelling
in aqueous media between a highly solvated, swollen gel state and a collapsed dehydrated network in response to a variation
of temperature. On the other hand, a significant phenomenon that was found in the gel swelling kinetics was an overshooting
under high temperature conditions. The presented hydrogels were used for release of model drugs that occur at the changes
of surrounding conditions, such as temperature and pH, in this study. It was also found that the higher the DN of AA, the
higher the gel transition temperature and the larger the release in a high temperature environment and, at the same time,
the larger the swelling ratios. |
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Keywords: | Hydrogel pH-thermoreversibility N-isopropylacrylamide-co-acrylic acid copolymeric gel Swelling ratio |
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